I say, and with Allah's help: The consideration in establishing the Sunnah of istinja with stones is cleanliness, not the number. If cleanliness is achieved with one stone, it suffices, and if it is not achieved with three, one may add more; does it not seem that if one used a stone with three edges, and used each edge until cleanliness was achieved, it is permissible by consensus among us? Abdullah ibn Mas'ud (may Allah be pleased with him) said: 'The Prophet (peace be upon him) went to relieve himself, and he ordered me to bring him three stones. I found two stones and sought the third, but I could not find it, so I took a piece of dung and brought it to him. He took the two stones and threw away the dung, saying: This is impure.' This is in Sahih al-Bukhari 1/70, and the wording is his. And in Sunan al-Tirmidhi 1/25, which al-Tirmidhi authenticated. The Prophet (peace be upon him) took the two stones and threw away the dung, and did not ask him for the third. If he did not ask for the third, it is clear that the number is not a condition; if it were a condition, he would have asked for the third. And from Abu Huraira (may Allah be pleased with him), he said: 'When one of you uses stones, let him use an odd number,' in Sahih Muslim 1: 212; and the least of the odd number is once. The command to use an odd number is not for its own sake but for achieving cleanliness. If cleanliness is achieved with less than three, the objective is fulfilled, and the ruling ends. Just as it is not permissible to make the pure impure without necessity. And from Anas ibn Malik (may Allah be pleased with him): '... A boy entered with him a place for washing, he was the youngest among us, and he placed it, then he covered it, and the Messenger of Allah (peace be upon him) relieved himself and came out to us after having used water for istinja,' in Sahih Muslim 1: 227. And from Ali ibn Abi Talib (may Allah be pleased with him): 'They used to use dung, and you are using water, so follow the stones with water,' in Sunan al-Bayhaqi al-Kubra 1: 106, and in Al-Athar 1: 7, and in Musannaf Ibn Abi Shaybah 1: 142. Refer to: Bada'i al-Sana'i, 1/19, and Tabyin al-Haqaiq, 1/77, and Al-'Inayah, 1/213, and Al-Bahr al-Ra'iq, 1/251, and Mukhtalif al-Riwayah, pp. 321-323, and Allah knows best.